While manufacturers claim that deer antler spray has vast benefits, scientists are skeptical.

"I’m 99% sure that eating deer antler to induce muscle growth won’t work," said Ethan Cohen, assistant professor in the department of endocrinology and metabolism at the University of Rochester. "But I have to admit it sounds good and will probably sell a lot of supplements."

IGF-1 is a protein that's naturally found in the human body. It's what makes children grow. So, in theory, ramping up the levels of IGF-1 in the system could potentially increase the number of cells with the ability to generate new muscle after exercise-induced injury. This means you can get stronger at a faster rate, explains Cohen.

The IGF-1 found in deer antler spray is derived from deer antler velvet, the tissue found inside the deer's antlers before they fully harden. Since deer antlers grow incredibly fast, it is not surprising that the horns are rich in IGF-1. This is a naturally-occurring form of IGF-1, meaning it is not made in a lab. As a result, deer antler velvet is considered a dietary supplement by the Food and Drug Administration, and unlike synthesized drugs, the product does have to be proven safe or effective before it's sold to the public.

The velvet is harvested in the early stage of growth by a veterinarian who clips the tips of the live antler. If not removed, the antlers will become very hard and sharp. The extract is frozen and then shipped to manufacturers that will turn it into a spray.

Lentini, the CEO of Nutronics Labs, a company that markets itself as selling the world's strongest and purest deer antler spray, claims to have introduced the elixir to the United States nearly two decades ago.

"We were the first to turn deer antler extract into a liquid spray," Lentini said.

WADA tested the company's lowest-strength deer antler spray to make their latest ruling, according to Lentini.

He claims that a quick spritz of his product under the tongue several times a day can help with countless ailments.

It can be used to recover from injuries, reduce inflammation in the brain from concussions, heal sprains or torn ligaments faster, speed up the metabolism, promote flexible joints, help build a healthier heart, and relieve arthritis, says Lentini, who has been administering the concoction into his mouth up to four times a day for 17 years.

The only side-effect to the product is that it raises your libido, Lentini added.

Scientists are skeptical

Deer antler spray sounds like a cure-all, but the scientific backing is flimsy at best.

Robert Libetti/ Business InsiderThe deer antler formula provided by Nutronics Labs has the essence of lemon and looked like dirty pond water.

Most of the product's medical benefits are based on testimonials from self-interested marketers like Lentini. The fitness guru sent us a sample of his strongest strength formula, 200,000 nanograms, in order to test it out for ourselves. The 2 fl. oz bottle sells for $189.99.

The product smells like lemon-scented cleaner and bears a resemblance to murky pond water. I hesitantly tried the stuff and found it surprisingly palatable, with a lemon taste, but not too sour and slightly sweet. The directions say to take 14 drops under the tongue, three times a day, but I stopped after one dose — so I probably don't have a good chance of reaping the benefits, if there are any.

While there's plenty of data that IGF-1 is a growth hormone in humans, the question is whether in a mouth spray it could make its way to our muscles intact. Even if IGF-1 dropped under the tongue makes it into the blood stream, data is lacking as to what impacts it has, if any.

Cohen has his own doubts about the ability of deer antler velvet to increase the levels of IGF-1, or any other growth factors, in the human body.

"Unlike steroids, which are small, cholesterol-based hormones, protein-based hormones or growth factors can easily be destroyed," he wrote in an email. Cohen guesses that even if you consume high levels of IGF-1, most if not all of the substance would be destroyed after hitting the acid in our stomach and before entering the blood system, which is how compounds we ingest reach the muscles. "This is also why you have to inject insulin instead of just eating insulin pills," he added.

But it sure sells well

At least it seems to be now. For awhile things were looking bad.

Lentini says his business was hit hard when, in 2011, the MLB placed deer antler spray on its list of cautionary products. This is partly because it contained IGF-1, and partly because it was causing players to test positive for the banned steroid methyltestosterone, although this is not an ingredient in the spray.

In any case, "people were canceling [orders] left and right," Lentini said.

WADA's new stance on deer antler spray has rolled back the tide, which in turn has been a great boon for manufacturers.

Since the agency lifted its ban, orders for Nutronics spray have started rolling in again.